The general aim of the investigation is to determine some of the factors that influence axonal growth in young animals during ontogenesis and in adults of lower vertebrate forms which have retained the capacity for regeneration in the central nervous system. The basic questions that underlie this study are: 1) under what conditions is axonal growth initiated, 2) what factors influence the elongation of the axon, and 3) what factors determine the establishment of synaptic connections between the growing axon and the cells with which it comes in contact. The answers to these questions are important for an understanding of the development dynamics of the embryonic and neonatal nervous system. They may also provide clues to procedures for promoting the repair of damaged nervous tissue, as might occur in stroke, spinal cord injury and birth injuries. Specific areas to be investigated include axonal transport of materials, morphological and metabolic characteristics of nerve cells with regenerating axons, and transfer of materials from one nerve cell to another. Experiments mainly involve use of radioactive tracers. BIBLIOGRAPHIC REFERENCES: Grafstein, B. The eyes have it: axonal transport and regeneration in the visual system. In: "The Nervous System, Vol. 1: The Basic Neurosciences". D.B. Tower, ed. Raven Press, New York. pp. 147-151, 1975. McQuarrie, I.G., B. Grafstein and M.D. Gershon. Regeneration of noradrenergic axons in rat sciatic nerve. Neurosci. Abstr. 1:777, 1975 (Abst.) $